Correct Answer - B
Infact the girl with normal vision is carrier because her father is colourblind (daughter of colurbind father are either colourblind or carrir ) and when she marries a normal man the possibly of their sons being colourblind is `50%` because the genotype of parents is XX and XY, so only half of the possible combinations of XY have the X - linked recessive gens which exhibit the disease.